Wood, a natural cellulose material, is used in home construction in roofing, frames, support and plywood; however, wood has use restrictions in roofing as there is no approved commercial fire resistant treatment. If homes were not protected with nonflammable roofs, a fire could easily jump from house roof to house roof, especially with high winds.
Effective fire resistant treatment of wood for both exterior and interior uses under conditions of leaching and weathering is needed because desirable properties of wood must be preserved after initial fire resistant treatment.
Fire retardants are added or applied to a cellulosic materials such as wood products to increase the resistance of that cellulosic material to fire. Such materials are less flammable than the cellulosic (wood) they protect. Some fire retardants prevent the spread of flame; others bun and thereby create a layer of char that inhibits further combustion. At the same time, some organic fire retardants may produce fairly toxic gases during exposure of the treated material to fire temperatures which may present problems for persons caught inside a burning building and for fire fighters.
The chemicals in a fire resistant composition determine how it works. Most flame retardants contain elements from any of three groups in the Periodic Table of Elements (Group IIIa (including boron and aluminum), Group Va (including nitrogen, phosphorus, arsenic, and antimony), and Group VIIa (including fluorine, chlorine, and bromine). Aluminum (sometimes as aluminum oxide) increase the amount of char formed in the early stages of a fire. This char forms a protective layer that prevents oxygen from reaching the inner layers of the protected material and thus sustaining the fire.
Phosphorus is a flame retardant in its solid and liquid phases which works by forming a surface layer of protective char on wood. Compounds of phosphoric acid are most frequently used as flame retardants for the first class of materials. On heating, sometimes phosphoric acid reacts with the cellulose to produce large amounts of carbon char and incombustible gases, such as steam and carbon dioxide, which either prevent fire from starting or smother it.
Various U.S. Patents disclose concepts for reportedly rendering wood flame proof. These patents include U.S. Pat. No. 4,981,518 issued to Melvin H. Sachs on Jan. 1, 1991 which discloses a cellulose filler material, such as wood chips, which are rendered nonflammable by encapsulation within a binder which is formed in an exothermic reaction from mixing a powdered base metal oxide and a weak acid, such as aluminum phosphate, which may be in the form of an acidic solution. This patent further discloses a method of making the bonded composite structure including the steps of mixing the weak acid and powdered base metal oxide, encapsulating the fibrous cellulose material within the binder and rendering the fibrous cellulose material nonflammable, thereby forming the slurry mixture into a predetermined form and setting the formed mixture into a solid.
U.S. Pat. No. 4,857,365 which issued to Shozo Hirao et al. on Aug. 15, 1989 and U.S. Pat. No. 4,731,265 which issued to Shozo Hirao et al. on Mar. 15, 1988 disclose a modified wood which is reportedly produced by reacting two water-soluble solutions, one with cations (selected from a group containing aluminum) and one with anions (from a group containing phosphoric acid) which react to form an insoluble, nonflammable, inorganic compound. A method of manufacturing a modified wood material is disclosed in these patents which reportedly can position within a raw wood material, an insoluble, nonflammable, inorganic compound using a highly efficient reaction achieved between cations and anions by sequentially immersing the raw wood material at least three times alternately in each of, and different one from that employed immediately before of a first water-soluble, inorganic substance solution containing cations and a second water-soluble, inorganic substance solution containing anions.
JP 63159008 discloses modified wood which is impregnated with insoluble, incombustible material using two aqueous solutions. A physical stimulus, which may be microwave heating, is given to the wood to promote formation of the insoluble material. Ions with a (3+) charge may be in one solution and phosphate ions in the other.
JP 48046195 discloses that pulp and wood are fireproofed with aluminum phosphate and silicates.
Aluminum phosphate has been manufactured in the United States since the late 1940s. While there is prior art as to compositions for fireproofing wood, including some compositions containing aluminum and some compositions containing phosphorus, a more efficient process and composition for fire resistant wood and rendering it leach resistant is provided herein using aluminum phosphate.